1. Field of the Invention
The present invention relates to an electrothermal color-varying instrument, and more particularly such instrument for inducing color change in a thermal color-varying layer provided in a toy, a picture book, a teaching aid, a writing board or the like.
2. Related Background Art
There is already proposed, for example in Japanese Laid-open Utility Model No. 62-139573 and Japanese Laid-open Patent No. 62-201128, an electrothermal heating instrument to be contacted with a thermal color-varying material provided on the surface of an animal toy or the like for varying the color of the contacted position.
Such conventional electrothermal heating instrument lacks, in the heat-generating element itself, the temperature self-controlling ability effective in a relatively low temperature range (about 70.degree. C. or lower), thereby involving danger of overheating and requiring therefore a temperature control switch or the like, and also necessitates insulation, for example with a ceramic material, for the heat-generating part in order to prevent the danger of current leakage.